202 University of California Publications in Zoology [Vol. 19 



observations, especially upon its metabolic character and nuclear 

 changes. The form has been identified as Collodictyon triciliatum 

 Carter (= Tetramitus sulcatus Stein). 



This genus was first described by Carter (1865, p. 289) as follows: 



Collodictyon, nov. gen. C. triciliatum, nov. sp. 

 Pyrifonn, straight, or slightly bent upon itself, bifid at the small extremity, 

 presenting at the larger one an indentation, from which spring three cilia. 

 Structure transparent, cancellated, composed of globular cells, with a strongly 

 marked, greenish granule here and there in the triangular spaces between them. 

 Locomotive, swimming by means of the cilia; subpolymorphic, flexible, yielding, 

 capable of assuming a globular form ... or one more or less modified by the 

 body it may incept . . . ; enclosing crude material for nourishment in stomachal 

 spaces, and ejecting the refuse, like Amoeba. Provided with a nucleus and 

 contracting vesicles. 



He gave its habitat (p. 289) as "fresh water, chiefly among Euglena 

 and Infusoria of that kind." Its length was 1/771 in. (30/i) and its 

 location the Island of Bombay. Among his observations he added 

 (p. 289) the following: "The plastic nature of this Infusorium, and 

 its mode of incepting food being like that of Amoeba (for it does not 

 appear to possess any oral aperture ) , induce me to think that it should 

 be placed among the Rhizopoda. Still it seems to have some analogies 

 to Boclo Ehr. " "Its generic name has been derived from its plasticity 

 and delicate cellular structure, which gives it a reticular or cancellated 

 appearance ; and its specific designation from the presence of three 

 cilia." 



The above description is satisfactory for identification, though not 

 detailed. My own observations coincide with it with these exceptions : 

 there are four instead of three flagella; it may or may not be bifid 

 at the posterior end; there is at the anterior end of the body a 

 blepharoplast from which the flagella arise, these not springing from, 

 but near the indentation, which is a continuation of the median groove, 

 or sulcus, which functions in food ingestion ; I have found no con- 

 tracting vacuole, though Carter stated that he had observed "contract- 

 ing vesicles" having no fixed position, but he figures none. 



In 1878 Stein figured a similar form, showing, however, the four 

 flagella, a median svdcus and a contractile vacuole, naming it Tetra- 

 mitus sulcatus. Kent (1880-1882, p. 314) accepted these organisms 

 as described by Carter and Stein as belonging to separate genera of 

 the family Trimastigiclae, but that there is little cause for such a 

 distinction can be seen from his characterization of Stein's genus as 

 follows : 



